Method of assembling pressure loaded gear pumps



Aug. 25, 1959 J. A. COMPTON METHOD OF ASSEMBLING PRESSURE LOADED GEAR PUMPS Original Filed July 19, 1950 Q "fnu erz i'or' I kfames' a. corn ion United States Patent METHOD OF ASSEMBLING PRESSURE LOADED GEAR PUMPS James A. Compton, South Euclid, Ohio, assignor to BorglqVarner Corporation, Chicago, 111., a corporation of liuois i 6 Claims. 01. 103126) This is a division of application Serial No. 174,606 of James A. Compton, filed July 19, 1950, now Patent No. 2,748,454, and entitled Method of Assembling Pressure Loaded Gear Pumps.

' This invention relates to a method of assembling pressure loaded type, intermeshing gear pumps, and to such pumps assembled according to this method.

In a pressure loaded, intermeshing gear type pump having one set of axially movable, pressure loadable bushings, a part of the output or discharge pressure of the pump is applied to the rear or motive surfaces of the axially adjustable bushings to urge these bushings into sealing engagement with their associated gears. As disclosed in US. Patent No. 2,420,622 to Roth et al., by carefully selecting the relative areas of the forward surfaces of the bushings and of the motive surfaces of the bushings, it is possible to control within very close limits the'actual sealing pressure provided. In practice, this requires a somewhat higher effective pressure in the direction of seal than in the direction tending to open the seal.

Because the pressure loadable bushings must be made movable a certain minimum clearance must be provided between the sides of the bushings and the adjacent sides of the chambers or bores in the pump housing in which the bushings are received. In practice, this clearance is actually very slight but it has been found that since the bushings may move either to one side or to the other of the chamber during assembly, occasionally a pump will be made in which the clearance of the bushings adjacent the inlet side of the pump is large enough, because of the corresponding reduction in clearance adjacent the discharge side of the pump due to lateral or transverse shiftingof the bushings, to provide a substantial leakage path to inlet pressure. This, of course, reduces proportionately the efiiciency of the pump.

An object of the present invention is to provide a new and improved method of assembling a pressure loaded type, intermeshing gear pump.

:A further object of the present invention is to provide aznew and improved pressure loaded type, intermeshing gear pump.

In accordance with this invention, a pressure loaded gear pump may be assembled by first inserting the axially movable, pressure loadable set of bushings in the main housing section in their usual position next to the intermeshing gears, and then pressing shims between the sides of the bushings and the wall of the housing chambers adjacent the discharge side so that the bushings are forced toward the inlet side of the housing. The cover housing section is then assembled on the pump body housing, omitting the usual sealing means. Then, with the parts held rigidly in position, a dowel hole is drilled through the flanged, mating portions of the two housing sections. Thereafter, the pump is disassembled, the shims removed, the usual sealing rings inserted and the pump reassembled. A dowel pin is inserted in the drilled hole and then the pump housing sections are bolted together. i

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The dowel pin maintains the position of the bushings established by the shims.

Other objects and advantages of the present invention will be apparent from the following detailed description thereof taken in conjunction with the drawings wherein:

Fig. 1 is a fragmentary, axial, sectional view of a pressure loadable type, intermeshing gear pump constructed in accordance with the method of this invention;

Fig. 2 is a transverse, sectional view taken substantially along the line'2-2 of Fig. 1 showing the shims in position against the bushings; and

Fig. 3 is a sectional view taken substantially along the lines 3-3 of Fig. 2, showing, however, the shims removed and a dowel pin in position.

Refering now to the drawings and particularly to Fig. 1 thereof, a pump generally similar to that shown in the aforementioned Roth et a1. patent is illustrated comprising a sectional housing having a main body portion 5 and a right closure member or cover member 6. These sections are normally bolted together as by the bolts 7 and cooperate to define therewithin a pair of parallel axis, intersecting bores or pumping gear chambers 8 and 9 which are arranged to receive in complementary relationship intermeshing pumping gears 10 and 11, respectively. In the embodiment illustrated, the pumping gears have integrally formed therewith hollow journal shafts 12 and 13, respectively, and the left portions of the journal shafts 12 and 13 are received in conventional flanged bushings 14 and 15 mounted in the left portions of the pumping gear chambers 8 and 9. The right portions of the gear journals are received, respectively, in axially adjustable, pressure loadable flanged bushings 16 and 17 mounted in the right side of the pumping gear chambers.

In the embodiment illustrated, the upper pumping gear 10 is the driving gear and is rotated in a clockwise direction, as viewed in Fig. 2. tional pump design practice the journal shaft of the upper gear may, therefore, be extended to the left, as viewed in Fig. 1, and coupled to a suitable power source. Low pres sure liquid is introduced into the pump housing at inlet 20 formed in the left side of the pump housing, as viewed in Fig. 2, and highpressure liquid is discharged from the pump housing through outlet 21 formed in the right side of the housing, the inlet and outlet ports communicating with the inlet and discharge areas of the intermeshing pumping gears. The pressure loadable bushings are normally fitted into the bores with sufiicient clearance to permit slight axial movement of the bushings with respect to the bores to establish the desired, pressure loaded seal during operation of the pump.

In the operation of a pump of this type, discharge pressure generated by the intermeshing gears may be com- H municated from the outlet or discharge side thereof to the annular pressure loading areas at the back of the bushing, designated 16-a and 17-a in the drawings through an axially extending passage 22 formed between the peripheries of the flanged portions of the bushings'on the discharge side of the pump at the point of convergence of the flanged portions of the bushings. Areas 16-a and 17zz.cooperate with the adjacent walls of the housing bores 8 and 9 and the peripheries of the barrel portions of the bushings 16 and 17 to define annular pressure loadf ing chambers 23 and 24, respectively. The passage 22 extends from the discharge side of the gears to the right; as viewed in Fig. 1, to the intercommunicating portions point of the pressure loading chambers 23 and 24 at their of juncture.

Escape of pressure rearwardly from the pressureloading surfaces is substantially prevented by means of an O-ring seal 25 disposed about the periphery of the rear or barrel portion of each-bushing in a suitable annular In accordance with conven-v diate pressure in accordance with conventional pressure loaded pump practice as set forth in the above-referenced Roth et al. patent.

Since it is necessary in order to permit the slight axial movement required of the bushings in order toestablish a seal, to lit the bushings with some clearance in the bushing receiving chambers the bushings may actually be assembled in such manner that more clearance is provided adjacent the inlet side of the pump than adjacent the discharge side of the pump, that is to say that the axially movable bushings may be slightly off-centered with respect to the axis of the bushing receiving chambers and located somewhat nearer the discharge port than the outlet port. Since, in the operation of the pump, the pressure applied to the pressure loading chambers 23 and 24- is substantially equivalent to discharge pressure, the leakage path provided by the excessive clearance occurring when the bushings are positioned nearer to the discharge port than to the inlet port may be sufiicient to materially reduce the efiiciency of the pump.

It has been found in accordance with the present invention that this undesirable condition. may be substantially eliminated by establishing the location of the bushings prior to final assembly of the pump in such manner that the clearance adjacent the inlet side of the pump is held to a minimum, and by providing means for maintaining this established relation after final assembly of the pump.

More particularly, in the assembly of the pump in accordance with the present invention, the bushings 14 and 15 are placed in the body housing section 5, the pumping gears 10 and 11 are then placed, in position with their left journal sections, as viewed in Fig. 1, received within the tubular portions of the bushings 14 and 15. Then, the axially movable pressure loadable bushings 16 and 17 are assembled in position on the pumping gears lit) and Ill, with their left sides in contact with the right side faces of the pumping gears. Thin, wedge-shaped members or shims 26 and 27' are then inserted between the sides of the flanged portions of the axially movable bushings l6 and 17 and the adjacent side walls of the pump receiving chambers 8 and 9 in the body housing section 5, the shims being located on the discharge port side of the pump body housing so as to move the bushings l6 and 17 against the opposite wall of the pump body housing, that is, the walls of the chambers nearer the inlet side of the pump. Preferably, the shims are spaced angularly from the discharge port, as shown in Fig. 2, so that the lines of force or directions of shift of the bushings tend to converge in the area of the inlet port, thus tending to position the bushing flanges so that the sides of the flanged portion contact closely the chamber walls in the area of the inlet.

The pump cover section 6 is then assembled into place on the pump body housing, omitting the usual sealing means, and the two housing sections are then clamped securely in position so that dowel holes 28 may be drilled through the flanged mating portions of the housing sections and 6. After drilling the dowel holes, the pump is disassembled, the shims removed and the pump reassembled, this time with the usual seals in place. Dowel pins 30 are then inserted in the drilled holes 28, thereby placing the two housing sections in the same relative positions which they occupied when the shims were used in the previous assembly operation. The holes and pins may be slightly tapered so that the pins may be wedged in place or the outer ends of the pins peened to secure the pins in the holes. The bolts 7 are then threaded into the housing sections and secured to complete the assembly of the pump.

As a result of this method of assembly, the finally assembled pump has the pressure loadable bushings located with the sides of their flanged portions contacting closely the adjacent walls of the pump chambers in the area of the inlet, thereby providing an effective seal and reducing to a minimum leakage in this area.

It will be understood that the actual shifting of the bushings by the shims is quite small and that the resultant displacement of the cover 6 with respect to the housing body section 5 is correspondingly slight. Accordingly, the usual clearance provided in the bolt-receiving holes in the pump housing is adequate to permit threading the bolts 7 into position despite the slight displace-v ment of the cover 6 from the conventional location with respect to the body section 5. Also, while a single. dowel pin and dowel hole may be employed, it will be evident that where two or more pins are employed with the pins spaced about the periphery of the housing a closer control of the location of the bushings is obtained.

In practice, it has been found that employing the invention not only materially reduces the numbers of rejects for failureto provide the required pumping efficiency but also permits wider tolerances in the fitting of the bushings in the pump. Heretofore, a bushing which was more than a slight amount smaller than the bore in which it was to be positioned had to be rejected because of the reduction in pumping efliciency that could result. The present invention, by establishing a minimum clearance in the area where leakage can be a factor, that is, the area adjacent the inlet or low pressure side of the pump, permits substantially greater latitude in the use of undersized bushings without serious loss in efliciency. Y

Where herein the various parts of this invention have been referred to as being located in a right or a left position, or an upper or a lower position, it will be understood that this is done solely for the purpose of facilitating description and that such references relate only to the relative positions of the parts as shown in the accompanying drawings.

What is claimed is:

1. A pressure loaded type intermeshing gear pump including a pumping cavity and at least one set of pressure loadable bushings having outer peripheral surface means and being adapted to engage the gear side faces in sealing relation, and a plural section housing enclosing said pump, means defining a chamber behind said bushings, means defining passage means for connecting pressure generated by said pump to said chamber whereby said bushings in response to said pressure in said chamber are moved into engagement with said gear side faces to provide said sealing relation, said pressure loadable bushings being disposed in one of said housing sections, said one housing section being slightly ofl-centered with respect to the other housing section so that the outer peripheral surface means of said pressure loadable bushings are in contact with the walls of said cavity in the area of said inlet thereby providing an effective seal and reducing to a minimum leakage in this area.

2. A pressure loaded type, intermeshing gear pump including a pumping cavity and at least one set of pressure loadable bushings having outer peripheral surface means and being adapted to engage the gear side faces in sealing relation, a plural section housing enclosing said pump, means defining a chamber behind said bushings, means defining passage means for connecting pressure generated by said pump to said chamber whereby said bushings in response to said pressure in said chamber are moved into engagement with said gear side faces to provide said sealing relation, said pressure loadable bush-- ings being disposed in one of said'housing sections, said one housing section being slightly oifwcentered with re-. sp-ect to the other housing section so that the outer Pfl'. ripheral surface means of said pressure loadable bush? ings are in contact with the walls of said cavity in the area of said inlet thereby providing an effective seal and reducing to a minimum leakage in this area, said house ing sections having a dowel hole formed therethrough and a dowel pin inserted in said hole forestablishing the elf-centered relation of said housing sections.

3. A fluid pump of the type including a housing having at least two sections, means defining a pumping cavity and an inlet and an outlet in said housing, said inlet leading to and said outlet leading from said cavity, a rotatable pumping member journalled in said housing for transferring fluid from said inlet through said cavity to said outlet, axially movable end plate means having outer peripheral surface means and being disposed in said housing and adapted to engage said pumping member in sealing relation, said end plate means together with said housing defining a pressure chamber behind said end plate means, means defining conduit means for continuously connecting pressure generated by said pump to said pressure chamber whereby said end plate means in response to the pressure in said pressure chamber is moved into engagement with said rotatable member to establish said sealing relationship, said end plate means being dis posed in one of said housing sections, said one housing section being slightly off-centered with respect to the other housing section so that the outer peripheral surface means of said end plate means are positioned more closely adjacent the Wall of said cavity in the area of the inlet than in the area of the outlet thereby reducing to a minimum leakage from said pressure chamber to said inlet in this inlet area.

4. A fluid pump of the type including a housing having a plurality of sections, means defining a pumping cavity and an inlet and an outlet in said housing, said inlet leading to and said outlet leading from said cavity, a rotatable pumping member journalled in said housing for transferring fluid from said inlet through said cavity to said outlet, axially movable end plate means having outer peripheral surface means and being disposed in said housing and adapted to engage said pumping member in sealing relation, said end plate means together with said housing defining a pressure chamber behind said end plate means, means defining conduit means for continuously connecting pressure generated by said pump to said pressure chamber whereby said end plate means in response to the pressure in said pressure chamber is moved into engagement with said rotatable member to 6 having a dowel hole formed therethrough and a dowel pin inserted in said hole for establishing the oil-centered relationship of said housing sections.

5. In a high prssure pump including a housing having a plurality of body sections and having a pumping cavity I with an inlet and an outlet, a bearing means for said cavity, said bearing means having an end plate portion provided with an outer peripheral surface means, said bearing means and said housing arranged to define a chamber behind said end plate portion, means providing a passage in communication with the pump discharge and said chamber whereby said end plate portion is urged toward the pumping cavity, said end plate portions beingdisposed in one of said body sections, said one body section being slightly off-centered with respect to the other body section so that said outer peripheral surface means of said end plate portion is positioned more closely adjacent the Wall of said cavity in the area of the inlet of the pump than in the area of said outlet thereby reducing to a minimum leakage from said chamber to said inlet in this inlet area.

6. In a high pressure pump including .a housing having a plurality of body sections and having a pumping cavity with an inlet and an outlet, a bearing means for said cavity, said bearing means having an end plate portion provided with an outer peripheral surface means, said bearing means and said housing arranged to define a chamber behind said end plate portion, means providing a passage in communication with the pump discharge and said chamber whereby said end plate portion is urged toward the pumping cavity, said end plate portions being disposed in one of said body sections, said one body section being slightly off-centered with respect to the other body section so that said outer peripheral surface means of said end plate portion is positioned more closely adjacent the Wall of said cavity in the area of the inlet of the pump than in the area of said outlet thereby reducing to a minimum leakage from said chamber to said inlet in this inlet area, and said body sections having a dowel hole formed therethrough and a dowel pin inserted in said hole for establishing the olfcentered relationship of said body section.

References Cited in the file of this patent UNITED STATES PATENTS 1,316,855 Olson Sept. 23, 1919 2,420,622 Roth et al. May 13, 1947 2,622,529 Parsons Dec. 23, 1952 2,632,400 Marsh Mar. 24, 1953 2,651,453 Le Febvre et a1. Sept. 8, 1953 

